linux-kernel - Re: [PATCH] media: v4l2-ctrls: add control for test pattern

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Message-ID: <20120903193947.GD6834@valkosipuli.retiisi.org.uk>
Date:	Mon, 3 Sep 2012 22:39:47 +0300
From:	Sakari Ailus <sakari.ailus@....fi>
To:	Prabhakar Lad <prabhakar.lad@...com>
Cc:	LMML <linux-media@...r.kernel.org>,
	dlos <davinci-linux-open-source@...ux.davincidsp.com>,
	linux-kernel@...r.kernel.org,
	Manjunath Hadli <manjunath.hadli@...com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-doc@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Hans de Goede <hdegoede@...hat.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Rob Landley <rob@...dley.net>,
	HeungJun Kim <riverful.kim@...sung.com>
Subject: Re: [PATCH] media: v4l2-ctrls: add control for test pattern

Hi Prabhakar,

Thanks for the patch.

On Mon, Sep 03, 2012 at 02:46:17PM +0530, Prabhakar Lad wrote:
> From: Lad, Prabhakar <prabhakar.lad@...com>
> 
> add V4L2_CID_TEST_PATTERN of type menu, which determines
> the internal test pattern selected by the device.
> 
> Signed-off-by: Lad, Prabhakar <prabhakar.lad@...com>
> Signed-off-by: Manjunath Hadli <manjunath.hadli@...com>
> Cc: Sakari Ailus <sakari.ailus@....fi>
> Cc: Hans Verkuil <hans.verkuil@...co.com>
> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Cc: Mauro Carvalho Chehab <mchehab@...radead.org>
> Cc: Sylwester Nawrocki <s.nawrocki@...sung.com>
> Cc: Hans de Goede <hdegoede@...hat.com>
> Cc: Kyungmin Park <kyungmin.park@...sung.com>
> Cc: Rob Landley <rob@...dley.net>
> Cc: HeungJun Kim <riverful.kim@...sung.com>
> Cc: Rob Landley <rob@...dley.net>
> ---
>  This patches has one checkpatch warning for line over
>  80 characters altough it can be avoided I have kept it
>  for consistency.
> 
>  Documentation/DocBook/media/v4l/controls.xml |   52 ++++++++++++++++++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls.c         |   16 ++++++++
>  include/linux/videodev2.h                    |   12 ++++++
>  3 files changed, 80 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
> index f704218..06f16e7 100644
> --- a/Documentation/DocBook/media/v4l/controls.xml
> +++ b/Documentation/DocBook/media/v4l/controls.xml
> @@ -4313,6 +4313,58 @@ interface and may change in the future.</para>
>  	      </tbody>
>  	    </entrytbl>
>  	  </row>
> +	  <row>
> +	    <entry spanname="id"><constant>V4L2_CID_TEST_PATTERN</constant></entry>
> +	    <entry>menu</entry>
> +	  </row>
> +	  <row id="v4l2-test-pattern">
> +	    <entry spanname="descr"> The capture devices/sensors have the capability to
> +	    generate internal test patterns. This test patterns are used to test a device
> +	    is properly working and can generate the desired waveforms that it supports.
> +	    </entry>
> +	  </row>
> +	  <row>
> +	    <entrytbl spanname="descr" cols="2">
> +	      <tbody valign="top">
> +	        <row>
> +	         <entry><constant>V4L2_TEST_PATTERN_DISABLED</constant></entry>
> +	          <entry>Test pattern generation is disabled</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_VERTICAL_LINES</constant></entry>
> +	          <entry>Generate vertical lines as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_HORIZONTAL_LINES</constant></entry>
> +	          <entry>Generate horizontal lines as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_DIAGONAL_LINES</constant></entry>
> +	          <entry>Generate diagonal lines as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_SOLID_BLACK</constant></entry>
> +	          <entry>Generate solid black color as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_SOLID_WHITE</constant></entry>
> +	          <entry>Generate solid white color as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_SOLID_BLUE</constant></entry>
> +	          <entry>Generate solid blue color as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_SOLID_RED</constant></entry>
> +	          <entry>Generate solid red color as test pattern</entry>
> +	        </row>
> +	        <row>
> +	          <entry><constant>V4L2_TEST_PATTERN_CHECKER_BOARD</constant></entry>
> +	          <entry>Generate a checker board as test pattern</entry>
> +	        </row>

You're defining 8 different test patterns based on a single device, I guess? 

As the test patterns are not standardised, I'd suppose that if another
driver implements the same control, it would require another n menu items
added to the same standard menu. That way we'd run quickly out of menu items
as the maximum is 32.

For this reason I'd leave the items in the menu up to the driver that
implements the control, until we have more information on the test patterns
different devices implement --- as discussed earlier.

Kind regards,

-- 
Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk
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